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GEOLOGIC RISK MANAGEMENT DURING AND AFTER THE FLOOD DISASTER OF 2005 (TYROL/AUSTRIA)
Thomas Figl1, Peter Gstrein2, Gunther Heissel3, Petra Nittel 4
On 22.08.2005, after several days of strong rain, heavy rainfall started. Saturation of bedrock was caused by heavy rainfalls in the days before 22.08.2007.
Because of this saturation the geologists of the local government contacted the specialists of the Hydrographic Service and the Alert Centre for Civil Protection and from this moment the geologists were in alert.
In the evening hours of 22.08.2005 first roads had to be closed and special procedures had to be decided for the safety of an emergency helicopter base.
At 5 a.m. the geologists of the local government were alerted by Alert Centre for Civil Protection and at 6 a.m. the first meeting of the operation controllers began.
With the first daylight several people had to be evacuated from the roofs of houses, which were trapped by the flood of the rivers. After this the geologists began their reconnaissance flights by helicopter. These flights took several days, combined with field investigations. One of the aims was the estimation of level of danger for the inhabitants as well as for the rescue- and recovery teams. Another aim was the documentation and assessment of the erosion- processes in the affected area.
Especially in the western part of Tyrol infrastructure, as traffic ways and houses were widely destroyed or damaged. As a result of the erosion processes caused by the flood a joinery was destroyed by a huge boulder of a debris flow and a worker was killed.
Also caused by the flood was the reactivation of a giant mass movement of a slope (Zintlwald) north of the river Rosanna on 24.8.2005. The speed of the movement increased during the next days and destroyed the only road connection (Fig. 1) to the western part of Austria (Vorarlberg) and to Switzerland. The electric cable of the Austrian railways was also destroyed. The railway to Switzerland was already interrupted due to erosive damages caused by the flood processes. As the speed of the mass movement reached velocities of several tens of centimetres a sudden sliding of wide spread parts of the slope, causing a slack flow of the river and a subsequent burst of the water, could not be excluded. More than a thousand people would be affected by such processes. Therefore it was necessary to start a geologic mapping of the mass movement immediately and to develop an effective monitoring programme.
Another reactivation of a mass movement was caused by the flood at the 29.08.2005.
Resulting from this a bridge (Gfällbrücke) of the only road to the biggest tourist centres in western Tyrol (Ischgl, Galtür) was endangered and had to be closed for some weeks (Fig. 2).
1Landesgeologe, Amt der Tiroler Landesregierung, Herrengasse 1-3, 6020 Innsbruck, Österreich (Tel.:
+43676885054321; thomas.figl@tirol.gv.at)
2Landesgeologe, Amt der Tiroler Landesregierung, Herrengasse 1-3, 6020 Innsbruck, Österreich (Tel.:
+43676885054319; peter.gstrein@tirol.gv.at)
3Landesgeologe, Amt der Tiroler Landesregierung, Herrengasse 1-3, 6020 Innsbruck, Österreich (Tel.:
+43676885054320; gunther.heissel@tirol.gv.at)
4 Landesgeologin, Amt der Tiroler Landesregierung, Herrengasse 1-3, 6020 Innsbruck, Österreich (Tel.:
+43676885054317; petra.nittel@tirol.gv.at)
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One of the most important points for the geologists of the local government was to inform the population about the risks, the evacuation plans and the recovery works. Another point was the administration of the scientific research programme to provide a base for recovery.
Today, at the beginning of 2007 and almost 30 month later, the problem of the mass movement of “Gfällbrücke” endangering the road to the cut off regions, is solved. The monitoring programme worked well so that the drilling of a bypass-tunnel (Fig. 4) was made possible. The bridge will be removed in spring 2007.
At “Zintlwald” the still working monitoring allows an exact assessment of the motion of the landslide. Meanwhile the moving slope is drained (Fig. 3) and the road is reopened.
Population is still briefed by the geologists and geoscientific research is still going on.
The team of the geologists of the local government guaranteed an efficient risk management and an efficient assistance for the population. This was the base for the confidence of the people in the taken measures.
Fig. 1: Destroyed road at „Zintlwald” 24.8.2005 Fig. 2: Rockfall at „Gfällbrücke” 29.08.2005
Fig. 3: Drained slope at „Zintlwald” 2006 Fig. 4: The new bypass-tunnel at Gfäll 2007
